Our general goal has been to extend our understanding of macromolecular processes that are involved in the regulation and control of various biological events. To this end we have been primarily concerned with the thermodynamic description of ligand-linked processes that are amplified into various macromolecular changes. The physical-chemical properties of respiratory proteins are particularly suited for these studies. Due to its accessibility and the extensive knowledge of its properties, hemoglobin continues to play a central role in ligand control studies: a) Continue examination of ligand induced phase changes as exhibited by HbS. Some effort will be directed towards the search for triple point conditions where solution phase is in equilibrium with oxygenated and deoxygenated crystal phases. Examine the effect of non-hybridizing proteins, such as serum albumin, upon HbS solubility. b) Conduct heats of reaction measurements with O2 and CO upon trout hemoglobins and hemocyanins in collaboration with M. Brunori. Conduct parallel studies of oxygen binding curves with our thin layer cell, and parallel measurements of Bohr effects in our drop titrator. If the techniques give the expected precision, then an effort will be made to determine heats of reaction and Bohr proton release values as a function of extent of reaction. c) Examine general effects of DPG and IHP on oxygen binding curves to HbA under high concentration hemoglobin conditions with fixed DPG or IHP content in collaboration with G. Ackers. Determine proton release values and binding constants of IHP binding from direct titrations measurements. Determine effect of CO2 on oxygen binding curves of HbA.